All our gliders have heavy duty ball bearings for a smooth, long, and squeak-free glide. We use twice the number of bearings and stand behind our product with life-time free replacement bearings. Seat cushions are supported with No-Sag springs. Seat cushions are filled with high density 4" polyurethane foam and backs are filled with soft polyester Dacron fiber which help achieve maximum comfort and durability. Frames are made of solid oak joinery for durability and strength; fully assembled with base detached for shipping. The base mounts to the top with 4 bolts .